Fisheye lens systems

ABSTRACT

A lens system comprises, in sequence moving from the object side, first and second negative meniscus lenses both convex to the object side, a biconvex lens, a negative meniscus lens cemented to the third lens, and fifth to eighth lenses including one or two negative lenses and cemented together so as to form two lens groups. An aperture stop is interposed between the fourth and fifth lenses. The lenses are arranged to satisfy predetermined conditions, thereby providing a fisheye lens system having a long back-focus two to three times greater than its focal length and yet having a compact construction.

United btatc Z 111 3,734,600 Shimizu K ii I 0 1 May 22, 1973 6/ s4 FISHEYE LENS SYSTEMS 3,524,697 8/1970 lsshiki et al ..350/l96 [75] Inventor: Yoshiyuki Shimizu, Kawasaki, FOREIGN PATENTS OR APPLICATIONS Japan 1,137,788 12/1968 Great Britain ..350/2l5 [73] Assrgnee: Nippon Kogaku K.K., Tokyo, Japan 22 Filed; 16, 1971 Primary Examinerlohn K. Corbin Attorney-Joseph M. Fitzpatrick et al. [21] Appl. No.: 208,639

[57] ABSTRACT ign Application Priority Data A lens system comprises, in sequence moving from the Dec 24 1970 J3 an 45/ 6645 object side, first and second negative meniscus lenses p both convex to the object side, a biconvex lens, a negative meniscus lens cemented to the third lens, and "350/196 gg s zg fifth to eighth lenses including one or two negative [58] Field 215 214 lenses and cemented together so as to form two lens 350/196 groups. An aperture stop is interposed between the fourth and fifth lenses. The lenses are arranged to [56] References Cited satisfy predetermined conditions, thereby providing a fisheye lens system having a long back-focus two to UNTED STATES PATENTS three times greater than its focal length and yet having a compact construction. 3,601,473 8/1971 Mandler ..350/2l5 3,497,291 2/1970 Woltche ..35 0/2l5 4 Claims, 14 Drawing Figures L3 L4 FILTER L5 L6 L7 L8 APERTURE R2 R3R4 STOP PATENIEDmzzmu 3 734,600

SHEET 1 OF 3 FIG. I

L3 L4 FILTER APERTUR STOP FIG. 2 FIG. 2 FIG. 2c

SPH RICAL SAGTAL QEE RAT'ON ASTIGMATISM msToRTlON CONDITION MERIDIONAI:- /2.8 7 9o I d g l I F/4 l PATENTEB HAY 2 21973 FIG. 5A

SPH RICAL ABEERATION SINE CONDITION sum 3 or 3 FIG. 5B

ASTIGMATISM FIG. 6&

SFHERICAL ABERRATION SINE CONDITION FIG. 6B

SAGITAL. ASTIGMATISM SAGITAL MERIDIONAL- FIG. 5C

DI STORTION -150 %T F G. 6C

DISTORTION 1 FISHEYE LENS SYSTEMS BACKGROUND OF THE INVENTION SUMMARY OF THE INVENTION The present invention seeks to realize a compact .optical system which has an aperture ratio of F/2.8 and also provides a back-focus which is two or more times longer than its focal length.

According to the present invention, there is provided a speed fisheye lens system which comprises, as viewed in the direction running from the object to the image,

first and second negative meniscus lenses both convex to the object side of the system, a third lens which is biconvex, a fourth lens which is a negative meniscus lens cemented to the third lens, fifth to eighth lenses including one or two lens groups, and an aperture stop interposed between the fourth and fifth lenses. The lens system is arranged to satisfy certain conditions to be described, and provide a back-focus two to three times longer than its focal length.

There has thus been outlined rather broadly the more important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will form the subject of the claims appended hereto. Those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures for carrying out the several purposes of the invention. It is important, therefore, that the claims be regarded as including such equivalent construction as do not depart from the spirit and scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS A specific embodiment of the invention has been chosen for purposes of illustration and description, and is shown in the accompanying drawings, forming a part of the specification, wherein:

FIGS. 1 and 3 are longitudinal sections of Examples I and II of the present invention; and

FIGS. 2(A), 2(8), 2(C), 4(A), 4(8), 4(C), 5(A), 5(B), 5(C), 6(A), 6(8), and 6(C) are graphs ofvarious aberration curves in Examples I, II, III and IV of the present invention, wherein FIGS. 2(A), 4(A), 5(A) and 6(A) show the spherical aberration (d and g indicate curves for the wavelengths of dand g-lines), FIGS. 2(8), 4(8), 5(8) and 6(3) show the astigmatism and FIGS. 2(C), 4(C), 5(C) and 6(C) show the distortional aberration.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIGS. I or 3, as viewed from object to image, a first lens L, and a second lens L, are meniscus lenses of negative focal length with their convex surfaces facing toward the object. A third lens L, is a biconvex lens, to which is cemented a fourth lens L, which is a negative meniscus lens. The fourth lens L, is followed by fifth, sixth, seventh and eighth lenses L L L and L respectively, and an aperture stop is interposed between the lenses L, and L,. A filter may further be interposed between the lens L, and the aperture stop. One or two of the four lenses L, to L, are negative lenses, and these last four lenses may be such that each two of them are cemented together to provide two lens groups as shown in FIG. 1, or that three of them are cemented together to divide the four lenses into two groups in the manner shown in FIG. 3.

Let the focal length of the entire lens system be f, the radius of curvature of the ith lens surface be R,, the inter-vertex distance of the ith lens be d,, the refractive index and the dispersive power of the jth lens L, be n, and v}, respectively. According to the invention then, the lens system must satisfy the following relations:

Also, let the mean value of the refractive indices and the mean value of the dispersive powers of the materials forming the concave lenses among the lenses L to L, be n,, and 11, respectively, and the mean value of the refractive indices and the mean value of the dispersive powers of the materials forming the convex lenses among the lenses L to L be ri and Vp, respectively. Then the following relation must also be satisfied:

The significances of the foregoing conditions will now be described.

Condition (1) relates to the radii of curvature R, and R, in the object-facing surfaces of the lenses L, and L,.

If the values of R, and R are lower than the lower lim- I its of condition l the effective apertures of the lenses L, and L, will be greater. If the radii of curvature R, and R exceed the upper limits of condition (I), light rays having wide angles of field will be incident on the object-facing surfaces of the lenses L, and L, at greater angles of incidence, thus resulting in an insufficient quantity of peripheral light. Thus, condition (I) is directed to reduce the dimensions of the lens system while securing a sufficient quantity of peripheral light.

Condition (2) is concerned with the radii of curvature R, and R, in the image-facing surfaces of the lenses L, and I..,. If the values of R, and R, are lower than the lower limits of this condition, off-axis rays incident with certain angles of field (i.e., rays incident at certain angles with the optical axis) will suffer from an excessive inner coma which cannot be corrected. Conversely, if the values of R and R, exceed the upper limits of condition (2), it will become difficult to attain a long backfocus. Thus, condition (2) is intended to prevent occurrence of any excessive coma while maintaining a long back-focus.

Condition (3) deals with the radius of curvature R in the image-facing surface of the lens L and prescribes a negative value for the radius of curvature R This condition is meant to correct the inner coma which may be produced in the off-axis rays incident on the lens L, at the angles of field provided by the imagefacing surfaces of the preceding lenses L and L Since the aperture stop is located rearwardly from the lens L such off-axis rays are subjected to greater refractions than the principal rays because of the limitations imposed upon the image-facing surface of the lens L and the said refractions occur in the direction for correcting the inner coma. Thus, condition (3) is useful to correct the coma.

Finally, condition (4) is meant for the correction of astigmatism and this calls for a lower mean refractive index for the positive lenses than for the negative lenses in the lens groups succeeding to the aperture stop. This is effective to render the Petzval sum positive, and useful to correct the deviation of the Petzval sum of the lenses L and L toward the negative. Condition (4) also calls for a greater mean dispersive power for the positive lenses than for the negative lenses in the same lens groups, and this is useful to correct the axial chromatic aberration and the chromatic difference of magnification which results from the lenses L and L Numerical data for the various examples of the present invention will be shown below. In the tables below, R represents the radius of curvature, vd the inter-vertex distance, n the refractive index, and vd the dispersive power. Although the arrangements of Examples I and 11 have been shown in FIGS. 1 and 3, those of Examples 111 and IV are omitted because they are similar to the arrangements of FIGS. 3 and 1, respectively.

Example 1 Focal length f=100.0, Angle of field 180, F/2.8,

Back-focus 237.38

The spherical aberration and s ine condition in the above Example are shown in FIG. 2 (A), and the astigmatism and distortional aberration are shown in FIGS. 2 (B) and 2 (C), respectively.

Example 11 Focal Length F1000, Angle of field 180, F/2.8,

Back-focus 246.08 A

The spherical aberration and sine condition in the foregoing Example are shown in FIG. 4 (A), and the astigmatism and distortional aberration are shown in FIGS. 4 (B) and 4 (C), respectively.

Example 111 Focal length F1000, Angle of field 180, F/2.8

Back-focus 240.33

The spherical aberration and sine condition in this Example are shown in FIG. 5 (A) and the astigmatism and distortional aberration are shown in FIGS. 5 (B) and 5 (C), respectively. Example 1V Focal length f=l00.0, Angle of field F/2.8

d =6.666 m, =1.52682 vd =51.1 R, #200000 d,,=33.333 n =1.52000 vd =70.1 R,,=-s3.333

The spherical aberration and sine condition in the above Example are shown in FIG. 6 (A) and the astigmatism and distortional aberration are shown in FIGS. 6 (B) and 6 (C), respectively.

It will thus be appreciated that the present invention can provide a compact, bright fisheye lens system having a long back-focus two to three times the total focal length thereof.

l claim:

1. A fisheye lens system comprising, as viewed in the direction from the object to the image, first and second negative meniscus lenses both convex to the object side, a third lens which is biconvex, a fourth lens which is a negative meniscus lens cemented to the third lens, fifth and sixth lenses and seventh and eighth lenses are cemented together, respectively, an aperture stop interposed between the fourth and fifth lenses, and a filter interposed between the fourth lens and the aperture stop, the lens system satisfying the following conditions:

Focal length f= 100.0, Angle of field 180, F/2.8,

Back-focus 237.38

where R represents the radius of curvature, d the inter vertex distance, n the refractive index, and 1 the dispersive power.

2. A fisheye lens system comprising, as viewed in the direction from the object to the image, first and second negative meniscus lenses both convex to the object side, a third lens which is biconvex, a fourth lens which is a negative meniscus lens cemented to the third lens, fifth, sixth and seventh lenses are cemented together, an eighth lens which is biconvex, an aperture stop interposed between the fourth and fifth lenses, and a filter interposed between the fourth lens and the aperture stop, the lens systern satisfying the following conditions:

Focal lengthf= 100.0, Angle of field 180, F/2.8,

Back-focus 246.08

where Rrepresents the radius of curvature, d the intervertex distance, n the refractive index, and v the dispersive power.

3. A fisheye lens system comprising, as viewed in the direction from the object to the image, first and second negative meniscus lenses both convex to the object side, a third lens which is biconvex, a fourth lens which is a negative meniscus lens cemented to the third lens, fifth, sixth and seventh lenses are cemented together, an eighth lens which is biconvex, an aperture stop interposed between the fourth and fifth lenses, and a filter interposed between the fourth lens and the aperture stop, in which the lens system satisfies the following conditions:

Focal length f= 100.0, Angle of field F/2.8,

Back-focus 240.33

where R represents the radius of curvature, d the intervertex distance, n the refractive index, and 1 the dis persive power.

4. A fisheye lens system comprising, as viewed in the direction from the object to the image, first and second negative meniscus lenses both convex to the object side, a third lens which is biconvex, a fourth lens which is a negative meniscus lens, fifth and sixth lenses and seventh and eighth lenses are cemented together, re-

Ki t-3333.333

R pl-ZGIOOO R..=-+s2o.00o

n,,-sa.a33

dfl3.333 4,-12000 1-5 I .333

Filter :FLS l 323 m-LSZOOO Filter vfSLl Iii-70.1

where R represents the radius of curvature, d the intervertex distance, n the refractive index, and v, the dis persive power. 

1. A fisheye lens system comprising, as viewed in the direction from the object to the image, first and second negative meniscus lenses both convex to the object side, a third lens which is biconvex, a fourth lens which is a negative meniscus lens cemented to the third lens, fifth and sixth lenses and seventh and eighth lenses are cemented together, respectively, an aperture stop interposed between the fourth and fifth lenses, and a filter interposed between the fourth lens and the aperture stop, the lens system satisfying the following conditions: Focal length f 100.0, Angle of field 180*, F/2.8, Back-focus 237.38 R1 +581.25 d1 17.5 n1 1.62041 Nu d 60.3 R2 +92.375 d2 70.0 R3 +546.875 d3 11.25 n2 1.62041 Nu d 60.3 R4 +95.625 d4 60.63 R5 +143.75 d5 45.62 n3 1.57501 Nu d 41.3 R6 -133.313 d6 10.0 n4 1.77279 Nu d 49.5 R7 -321.313 d7 3.13 d8 11.25 Filter n 1.51823 Filter d9 54.37 R8 +3312.5 d10 6.25 n5 1.52682 Nu d 51.1 R9 +200.0 d11 31.56 n6 1.5200 Nu d 70.1 R10 -173.75 d12 0.625 R11 +577.688 d13 31.25 n7 1.5200 Nu d 70.1 R12 -80.625 d14 5.63 n8 1.7552 Nu d 27.5 R13 -204.319 where R represents the radius of curvature, d the intervertex distance, n the refractive index, and Nu d the dispersive power.
 2. A fisheye lens system comprising, as viewed in the direction from the object to the image, first and second negative meniscus lenses both convex to the object side, a third lens which is biconvex, a fourth lens which is a negative meniscus lens cemented to the third lens, fifth, sixth and seventh lenses are cemented together, an eighth lens which is biconvex, an aperture stop interposed between the fourth and fifth lenses, and a filter interposed between the fourth lens and the aperture stop, the lens system satisfying the following conditions: Focal length f 100.0, Angle of field 180*, F/2.8, Back-focus 246.08 R1 +620.463 d1 15.873 n1 1.62041 Nu d 60.3 R2 +103.244 d2 76.190 R3 +438.095 d3 14.603 n2 1.62041 Nu d 60.3 R4 +89.206 d4 86.984 R5 +200.0 d5 53.333 n3 1.74950 Nu d 35.0 R6 -98.667 d6 24,126 n4 1.64831 Nu d 33.8 R7 -450.793 d7 3.174 d8 11.428 Filter n 1.51823 Filter d9 43.809 R8 +1666.667 d10 23.492 n5 1.51835 Nu d 60.3 R9 -79.619 d11 5.714 n6 1.74950 Nu d 35.0 R10 +151.111 d12 26.031 n7 1.5200 Nu d 70.1 R11 -156.317 d13 0.634 R12 +506.730 d14 17.778 n 1.5168 Nu d 64.2 R13 -218.876 where Rrepresents the radius of curvature, d the intervertex distance, n the refractive index, and Nu dthe dispersive power.
 3. A fisheye lens system comprising, as viewed in the direction from the object to the image, first and second negative meniscus lenses both convex to the object side, a third lens which is biconvex, a fourth lens which is a negative meniscus lens cemented to the third lens, fifth, sixth and seventh lenses are cemented together, an eighth lens which is biconvex, an aperture stop interposed between the fourth and fifth lenses, and a filter interposed between the fourth lens and the aperture stop, in which the lens system satisfies the following conditions: Focal length f 100.0, Angle of field 180*, F/2.8, Back-focus 240.33 R1 +620.463 d1 15.873 n1 1.62041 Nu d 60.3 R2 +103.244 d2 73.015 R3 +400.190 d3 14.603 n2 1.62041 Nu d 60.3 R4 +87.460 d4 90.158 R5 +189.968 d5 53.333 n3 1.744 Nu d 44.9 R6 -103.244 d6 23.492 n4 1.62041 Nu d 60.3 R7 -481.980 d7 3.174 d8 11.428 Filter n 1.51823 Filter d9 42.539 R8 +1666.667 d10 20.952 n5 1.51835 Nu d 60.3 R9 -75.936 d11 5.714 n6 1.74950 Nu d 35.0 R10 +148.571 d12 26.031 n7 1.52000 Nu d 70.1 R11 -156.317d13 0.634 R12 +506.730 d14 17.777 n8 1.51680 Nu d 64.2 R13 -219.993 where R represents the radius of curvature, d the intervertex distance, n the refractive index, and Nu d the dispersive power.
 4. A fisheye lens system comprising, as viewed in the direction from the object to the image, first and second negative meniscus lenses both convex to the object side, a third lens which is biconvex, a fourth lens which is a negative meniscus lens, fifth and sixth lenses and seventh and eighth lenses are cemented together, respectively, an aperture stop interposed between the fourth and fifth lenses and a filter interposed between the fourth lens and the aperture stop, in which the lens system satisfied the following conditions: Focal length f - 100.0, Angle of field 160*, F/2.8, BacK-focus 240.69 R1 +548.000 d1 16.0 n1 1.62041 Nu d 60.3 R2 +92.400 d2 70.0 R3 +578.000 d3 11.333 n2 1.62041 Nu d 60.3 R4 +93.866 d4 60.667 R5 +144.000 d5 49.333 n3 1.57501 Nu d 41.3 R6 -133.333 d6 13.333 n4 1.77279 Nu d 49.5 R7 -321.333 d7 3.333 d8 12.000 Filter n 1.51823 Filter d9 51.333 R8 +3333.333 d10 6.666 n5 1.52682 Nu d 51.1 R9 +200.000 d11 33.333 n6 1.52000 Nu d 70.1 R10 -180.000 d12 0.666 R11 +520.000 d13 33.333 n7 1.52000 Nu d 70.1 R12 -83.333 d14 3.333 n8 1.75520 Nu d 27.5 R13 -212.057 where R represents the radius of curvature, d the intervertex distance, n the refractive index, and Nu d the dispersive power. 